Angle Sideways Spinning Liquid Probes

MAGIC ANGLE SIDEWAYS SPINNING LIQUID PROBES 

The ability of the Nano-probe to put 100% of the sample in the rf coil of the probe makes it useful for acquiring data on trace samples such as metabolites and 

Aside from the obvious improvement in the s/n ratio, which arises in part from concentrating the sample from 145 to 40 pL as well as from having all of the sample in the rf coil rather than 70%, the ketone carbonyl resonance at 219.5 ppm was observed with reasonable signal intensity whereas its presence was questionable at best in the 3 mm micro-dual probe 13C spectrum shown in the top panel. The s/n ratios of the overnight acquisitions were 5.5 1 for the 3 mm micro-dual probe vs. 11 1 for the Nano-probe . There is no obvious reason why the carbonyl resonance was not observed in the 3 mm micro-dual 13C spectrum, as the relaxation delay between acquisitions was set identically in the two experiments. These data also suggest that on a per-transient basis, that the performance of the Nanoprobe is perhaps somewhat lower than that of the 3 mm micro-dual probe. This inference is based on the nearly 4-fold concentration difference between the two probe formats. Assuming probe efficiencies were identical, an s/n ratio approaching 22 1 should have been observed for the Nano-probe based on the concentration increase. 

One other application where Nano-probe technology excels relative to conventional tube or flow NMR probe formats is in the area of heterogeneous samples. One of the early applications demonstrated for the Nano-probe was the acquisition of NMR spectral data for chemically modified polymer beads used in solid-phase-assisted peptide synthesis and related chemical transformations.21 23 When chemically modified beads are interrogated in a conventional NMR sample tube, the resin bead behaves as an insoluble material and at best very broad and poorly resolved spectra may be recorded. In contrast, when the same beads are placed in a Nano-probe and spun at several kHz at the magic angle, there is sufficient solvation of the pendant chemical moiety and the linker to resin bead nucleus to allow the modified portion to behave as if it is in pseudo solution, which allows reasonable NMR spectra to be recorded. Various factors affect the quality of the NMR data that can be obtained for the pendant molecule, which include the tether length and the solvent used for the measurement.23 There have been a diverse assortment of applications of Nano-probe applications reported in the literature that are discussed in further detail in Section 6.3. 

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Magic Angle Sideways Spinning Liquid Probes 16... 

MAGIC ANGLE SIDEWAYS SPINNING LIQUID PROBES... 

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